1. Field of the Invention
The present invention is related to the field of bird feeders and, more particularly, to an airtight-sealing cap or cover for a top-fill hummingbird feeder.
2. Description of the Related Art
People who live in an area inhabited by hummingbirds frequently try to promote their presence by the use of hummingbird feeders. Hummingbird feeders differ from ordinary bird feeders because hummingbirds feed on nectar or simulated nectar, which are liquid, instead of the seeds or other dry food consumed by most birds from bird feeders. Simulated nectar is typically formed from water sweetened with sugar or honey. In many hummingbird feeders, the nectar (or simulated nectar) is stored in a reservoir and conveyed to simulated flowers where a perch may be provided so that the hummingbird can land and, having a long, slender beak, insert it into the access apertures in the simulated flower and feed.
Most hummingbird feeders have one of two basic designs. One includes an inverted top container which empties into a lower reservoir or feeding basin from which the birds feed. The vacuum at the top of the container (or put another way, the outside air pressure) keeps the liquid in the top container from draining too rapidly out of the feeding basin. The other common feeder design consists of a container with holes in its cover through which the hummingbirds reach to feed. This latter style of feeder suffers from the problem that it must be refilled very often, because the level of food is constantly being reduced by the feeding.
The so-called “vacuum-type” feeders also have problems. For example, they can only be filled by dismantling the feeder and removing the top container from its feeding position. Ordinarily, the consumer must invert the feeder in order to refill it, with the attendant risks of spillage, and requires a certain amount of manual dexterity to create the necessary vacuum. Moreover, because a vacuum is required, these designs are limited to a single opening for filling and cleaning. This opening is typically small, which restricts access to the interior of the container and makes it more difficult to effectively clean the container. Additionally, vacuum feeders can corrode or be inefficient, permitting the nectar to leak and creating an increased risk of insect contamination.
One product which has been available in the market is the Garden Song Top Fill Hummingbird Feeder from Opus Incorporated, now marketed by the assignee of the instant invention. The Opus feeder, described in U.S. Pat. No. 7,600,487 (“the '487 patent”) includes an upstanding liquid container with a large top opening and a small cylindrical lower opening which is screw-threaded into an upstanding cylindrical collar positioned in the center of a feeding basin or liquid tray. The top opening is closed with a cover that seals the container to create a vacuum as the liquid level recedes downwardly in the container. An internal, rotatable ring or valve mechanism has an upstanding cylindrical wall which surrounds the aforesaid cylindrical collar inside the feeding basin.
Another top-fill style hummingbird feeder is set forth in copending application, Ser. No. 12/213,924 (“the '924 application”), also owned by the assignee of the instant invention. This hummingbird feeder includes a generally upstanding reservoir bottle having a large opening at its top end that is sealed by a removable top or cap. The bottom of the bottle or container has a lower bottom opening which can be screw-threaded into a central collar of a feeding basin that has a plurality of feeding ports in a known arrangement. As a representative top-fill hummingbird feeder with which the cap of the present invention may be used, the '924 application is hereby incorporated by reference in its entirety as if fully set forth herein.
One problem associated with top fill hummingbird feeders such as those described above is the removable top or cap which must reliably form an airtight seal over the top opening of the reservoir bottle so that the necessary vacuum is formed and maintained above the liquid nectar retained in the bottle. If the removable cap is not properly designed to form the requisite airtight seal or cannot be reliably manipulated by the user to form such airtight seal, the top fill hummingbird feeder will not operate properly.